Today, people often interact with networked environments or online services. Many users of computing devices (or systems) frequently browse web sites, access online content, or otherwise use network services. Users with access to the Internet can perform online shopping, play or stream media, download software, utilize social networking services, and accomplish many other tasks. In one example, users of a social networking service or system can publish advertisements, purchase applications, give gifts, distribute promotions, or conduct various other transactions. Sometimes, an illegitimate user can attempt to publish illegitimate (e.g., fraudulent, fake, illegal, etc.) advertisements or conduct other illegitimate actions. In another example, users can provide their payment or financial information to an online service in order to fund various online activities. However, at times, an illegitimate user can attempt to illegitimately gain access to a legitimate user's information or otherwise compromise the legitimate user's account with the online service.
Accordingly, when a user of an online service, such as a social networking system, participates in various activities that involve the use of financial instruments compatible with the online service, the financial instruments of the user can sometimes be stolen, illegitimately used, or otherwise compromised. Moreover, in some cases, an illegitimate user can attempt to illegitimately avoid paying for his or her use of the online service. These and other similar concerns can reduce the overall user experience associated with online services.